Radiobiological model comparison of 3D conformal radiotherapy and IMRT plans for the treatment of prostate cancer

Full text: The main aim of radiotherapy is to deliver a dose of radiation that is high enough to destroy the tumour cells while at the same time minimising the damage to normal healthy tissues. Clinically, this has been achieved by assigning a prescription dose to the tumour volume and a set of dose constraints on critical structures. Once an optimal treatment plan has been achieved the dosimetry is assessed using the physical parameters of dose and volume. There has recently been an interest in using radiobiological parameters to evaluate and predict the outcome of a treatment plan in terms of both a tumour control probability (TCP) and a normal tissue complication probability (NTCP). In this study, a radiobiological model ha> been used to compare a three dimensional conformal radiotherapy treatment (3D-CRT) and an intensity modulated radiotherapy (IMRT) of the prostate. There has been some debate in the literature about the value of ct/'P ratio that should be used to model the response of a prostate tumour to radiation. We investigate the sensitivity of the model to the a'(3 ratio used, for the prostate and also the sensitivity of the model to inter-observer variability at the planning stage.